Express dependency on py-expat.

(The python world seems to think that xml parsing functions are part
of core Python and need not be mentioned.  Perhaps pkgsrc's way of
having py-expat is unusual and a bit of DESCR spiffage is in order,
but I'm not sure what's right.)

devel/py-darcsver/Makefile

@@ -1,8 +1,9 @@
-# $NetBSD: Makefile,v 1.1.1.1 2010/07/24 15:15:10 gdt Exp $
+# $NetBSD: Makefile,v 1.2 2010/09/26 13:53:47 gdt Exp $
 #
 
 DISTNAME=	darcsver-1.5.1
 PKGNAME=	${PYPKGPREFIX}-${DISTNAME}
+PKGREVISION=	1
 CATEGORIES=	devel
 MASTER_SITES=	http://pypi.python.org/packages/source/d/darcsver/
 
@@ -11,6 +12,8 @@ HOMEPAGE=	http://pypi.python.org/packages/source/d/darcsver/
 COMMENT=	Generate a version number from darcs history
 LICENSE=	modified-bsd
 
+DEPENDS+=		${PYPKGPREFIX}-expat>=0:../../textproc/py-expat
+
 PKG_DESTDIR_SUPPORT=	user-destdir
 
 USE_LANGUAGES=	# none